I believe that I'm the right person for this job. I must kindly ask You to checkout some of my previous work and to tell me is there anything specific that You like and that can be used for Your purpose??
https://www.freelancer.com/u/frik53
I have many years of experience in graffiti, I painted on almost every possible surface, with different people, on different places, easily accessible and totally unavailable, legal and illegal, as well as on various events... I can send my graffiti related work, if needed...
...so, if you like anything, feel free to contact me, anytime!